Swift 'open' keyword & overridable method/properties in extension?

Question

With introduction of open keyword in Swift 3.0 (What is the \'open\' keyword in Swift?).

Note: Limited to extensions on NSObject derived classes

Answer 1

Unless I am mistaken, you can declare the extension methods as open in your framework if you just omit the public keyword in the extension declaration:

extension UIManagedDocument {

    open class func primaryDocumentName() -> String {
        return "Document"
    }
    // ...
}

And then (for NSObject subclasses or @objc members) you can override the method in your custom subclass in the main application (or in any module):

class MyManagedDocument: UIManagedDocument {

    override class func primaryDocumentName() -> String {
        return "MyDocument"
    }
    // ...
}